[firedrake] RT/BDM works but not TH/VMS

[Justin Chang]

Silly me

For VMS and TH I had to apply the homogeneous boundary conditions strongly.
TH is stable, at least from my experience (although not preferred since it
is not mass conservative). And yes I wrote the VMS formulation incorrectly,
there is a minus sign indeed.

Thanks,
Justin

On Fri, Nov 13, 2015 at 3:07 PM, Lawrence Mitchell <
lawrence.mitchell at imperial.ac.uk> wrote:

>
> On 13 Nov 2015, at 20:34, Justin Chang <jychang48 at gmail.com> wrote:
>
> V = VectorFunctionSpace(mesh,"CG",1)
> Q = FunctionSpace(mesh,"CG",1)
> W = V*Q
> v,p = TrialFunctions(W)
> w,q = TestFunctions(W)
> ...
> a = (dot(v, w) - p*div(w) - div(v)*q)*dx + 0.5*dot(v+grad(p),w+grad(q))*dx
> L = f*q*dx
>
> if that's what you're asking
>
>
> Plausibly also your boundary conditions are not applied correctly.
>
> In the hdiv-L2 formulation I would apply the pressure bcs weakly. But
> they're homogeneous, so those surface integral a vanish. Because the spaces
> match correctly this is enough. In the TH or VMS formulation to you have to
> explicitly apply the bcs strongly to the pressure variable?
>
> Lawrence
>
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